PaxosStore

Abstract

In this paper, we present PaxosStore, a high-availability storage system developed to support the comprehensive business of WeChat. It employs a combinational design in the storage layer to engage multiple storage engines constructed for different storage models. PaxosStore is characteristic of extracting the Paxos-based distributed consensus protocol as a middleware that is universally accessible to the underlying multi-model storage engines. This facilitates tuning, maintaining, scaling and extending the storage engines. According to our experience in engineering practice, to achieve a practical consistent read/write protocol is far more complex than its theory. To tackle such engineering complexity, we propose a layered design of the Paxos-based storage protocol stack, where PaxosLog, the key data structure used in the protocol, is devised to bridge the programming-oriented consistent read/write to the storage-oriented Paxos procedure. Additionally, we present optimizations based on Paxos that made fault-tolerance more efficient. Discussion throughout the paper primarily focuses on pragmatic solutions that could be insightful for building practical distributed storage systems.